Added basic normalization for IntExpressions

Summary:
+ There is no normalization on top of the abstract type support currently implemented.
+ We do not do any normalization, we just return the same polynomial.
+ Implemented just the basic polynomial normalization. Added some test cases showing what it does and does not do.
Currently, it eliminates zero-coefficient terms, and does not regard the order of monomials or terms in the monomial.

It does not collect like terms, either monomials or monomial factors.

Reviewed By: pradeep90

Differential Revision: D28890914

fbshipit-source-id: 8a887b961e94fcdfbb9ddf8c12d744778f3e7547

Author: Brandon Wu

source/analysis/test/typeTest.ml

@@ -1958,6 +1958,27 @@ let test_convert_all_escaped_free_variables_to_anys _ =
   ()
 
 
+let test_int_expression_create _ =
+  let x = Type.Variable.Unary.create "x" in
+  let y = Type.Variable.Unary.create "y" in
+  let assert_create_list_list given expected =
+    match Type.IntExpression.create (polynomial_create_from_variables_list given) with
+    | Type.IntExpression (Data result_polynomial) ->
+        assert_equal
+          ~printer:[%show: Type.type_t Type.Polynomial.t]
+          ~cmp:[%equal: Type.type_t Type.Polynomial.t]
+          result_polynomial
+          (polynomial_create_from_variables_list expected)
+    | _ -> assert false
+  in
+  assert_create_list_list [1, [x, 1]; 1, []; -1, []] [1, [x, 1]; 1, []; -1, []];
+  assert_create_list_list [1, [y, 1; y, 1]] [1, [y, 1; y, 1]];
+  assert_create_list_list [0, [x, 1; y, 1]; 0, []; 1, []] [1, []];
+  assert_create_list_list [1, [x, 1]; 1, [y, 1]] [1, [y, 1]; 1, [x, 1]];
+  assert_create_list_list [1, [x, 1; y, 1]] [1, [y, 1; x, 1]];
+  ()
+
+
 let test_replace_all _ =
   let free_variable = Type.Variable (Type.Variable.Unary.create "T") in
   let annotation = Type.parametric "p" ![free_variable; Type.integer] in
@@ -3572,6 +3593,7 @@ let () =
          "contains_escaped_free_variable" >:: test_contains_escaped_free_variable;
          "convert_all_escaped_free_variables_to_anys"
          >:: test_convert_all_escaped_free_variables_to_anys;
+         "int_expression_create" >:: test_int_expression_create;
          "replace_all" >:: test_replace_all;
          "less_or_equal_polynomial" >:: test_less_or_equal;
          "collect_all" >:: test_collect_all;

source/analysis/type.ml

@@ -728,6 +728,8 @@ and Polynomial : sig
 
   val create_from_int : int -> 'a t
 
+  val normalize : compare_t:('a -> 'a -> int) -> 'a t -> 'a t
+
   val create_from_variables_list
     :  compare_t:('a -> 'a -> int) ->
     (int * ('a Record.Variable.RecordUnary.record * int) list) list ->
@@ -994,7 +996,8 @@ end = struct
     | NonPolynomial of 'a Polynomial.t
     | Polynomial of 'a t
 
-  let normalize_variant ~compare_t:_ polynomial = Polynomial (Data polynomial)
+  let normalize_variant ~compare_t polynomial =
+    Polynomial (Data (Polynomial.normalize ~compare_t polynomial))
 end
 
 open Record.Callable